Advancing pharmaceutical effectiveness and safety in the United States requires reliable information regarding patterns of pharmaceutical use. The need for better information is particularly pressing regarding pediatric inpatient pharmaceuticals and over-the-counter (OTC) products, especially acetaminophen (APAP) (RFA-HS-08-005, Topic Area 4: Characterization of Key National Drug Use Scenarios). In a joint collaboration of the Centers for Education and Research on Therapeutics at The University of Pennsylvania and the M.D. Anderson Cancer Center, we propose to a) combine detailed but under-utilized existing large datasets and b) [unreadable] collect new primary data, which together will advance our ability to describe, study, and understand the [unreadable] effectiveness and safety of pharmaceuticals received by pediatric patients in hospitals, and how to improve the safe use of OTC APAP in home settings. The work we propose is divided into 2 projects. In Project I, our specific aims are to 1) Determine the rate of use of all pharmaceuticals used during pediatric hospitalizations in 2 large pediatric hospitalization databases containing pharmacy data, specifically the Pediatric Health Information System (PHIS) and Premier datasets; 2) Describe hospital-day specific rates of use, hospital day of first exposure to a drug, and concomitant drug exposures for the most commonly used drugs; 3) Use the nationally representative H-CUP Kids Inpatient Database to assess potential bias in the estimated rates of use of drugs used during pediatric hospitalizations based on the PHIS and Premier datasets; and 4) Examine among a cohort of children hospitalized for APAP overdose the patterns of receipt of an APAP overdose antidote the dose of which is titrated depending upon the extent of liver injury, thus providing a sign of the severity of APAP toxicity. Project II will be conducted in 3 phases. First, we will use focus groups to qualitatively explore knowledge, attitudes, beliefs, and practices of 5) a broadly representative sample of adults and adolescents regarding self-administration of OTC APAP, and parental administration of OTC APAP to children, and 6) a sample of key professional informants, including physician and pharmacists, with respect to communicating information on the administration and risks of OTC APAP to consumers and patients. Second, in phase 2, we will conduct a cross-sectional split-sample experimental survey to 7) estimate frequency of use, knowledge, and practices regarding use of OTC acetaminophen, and evaluate potential determinants of misuse in community-based samples. In Phase 3, we will 8) review medical records of Emergency Room visits to ascertain which events surround APAP overdosing. [unreadable] [unreadable] [unreadable]